In the fabrication of semiconductor devices, various semiconductor processes such as film formation, etching, heating, modification, and crystallization are repetitively performed on a target substrate such as a semiconductor wafer. In these semiconductor processes, a target substrate is placed on a worktable (susceptor) which is disposed in a process container, and the substrate is processed in this state. A lifting mechanism is used to transfer the target substrate with respect to the worktable. Generally, a lifting mechanism of this sort has lifter pins arranged one by one in through holes formed in the worktable.
FIG. 8 is a sectional side view showing a portion of a substrate lifting mechanism in a conventional semiconductor processing apparatus. As shown in FIG. 8, a plurality of through holes (guide holes) 150 are formed to vertically extend through a worktable 138. A lifter pin 152 is inserted into each guide hole 150 so as to be able to protrude and retract. The lifter pin 152 is driven by a predetermined driving means to protrude and retract with respect to the mount surface of the worktable 138 (e.g., Jpn. Pat. Appln. KOKAI Publication No. 6-318630).
In this lifting mechanism of a target substrate, a target substrate W is lifted from the mount surface by protruding the lifter pin 152 above the mount surface of the worktable 138 by the driving means. Also, the target substrate W is placed on the mount surface by moving the lifter pin 152 downward. Referring to FIG. 8, the lower end of the lifter pin 152 is supported as it simply abuts against the surface of a pin base 156 attached to a driving member 154. The lifter pin 152 is vertically moved inside the guide hole 150 by vertically moving the driving member 154.
PCT (WO) No. 2002-530847 also discloses a processing apparatus including a substrate lifting mechanism. In the apparatus of this reference, auxiliary pipes for guiding lifter pins are arranged inside through holes formed in a worktable.